JAMES M.GRICHNIKMD, PhD
The lesions shown in this article are from the upper lip of an 85-year-old woman (Figure 1, inset), the malar of a 67-year-old man (Figure 2, inset), and the forehead of a 56-year-old man (Figure 3, inset). They correspond to actinic keratosis (AK) (case 1), lichenoid AK (case 2), and squamous cell carcinoma that developed on an AK (case 3). Polarized contact dermoscopy of all 3 lesions revealed a pattern called a rosette sign (Figures 1-3, arrows), a term coined by Lester Cowell, MD, and is characterized by 4 white points arranged as a 4-leaf clover (Figure 4) mainly localized inside the follicular openings. Histologically, the rosette sign may correspond to changes of orthokeratosis and parakeratosis (flag sign) (Figure 5 [case shown in Figure 3]). It is occasionally seen in AK and related conditions and could help in their diagnosis. It does not appear in nonpolarized contact dermoscopic images and may therefore represent a tissue and polarized light phenomenon.
Cuellar F, Vilalta A, Puig S, Palou J, Salerni G. New Dermoscopic Pattern in Actinic Keratosis and Related Conditions. Arch Dermatol. 2009;145(6):732. doi:10.1001/archdermatol.2009.86